It will be remembered that Smith had not yet discovered what became of the surplus water of the lake, and as there was no indication of its ever overflowing, an outlet must exist somewhere. He was surprised, therefore, on noticing a slight current just at this place. Throwing in some leaves and bits of wood, and observing their drift, he followed this current, which brought him to the southern end of the lake. Here he detected a slight depression in the waters, as if they were suddenly lost in some opening below. Smith listened, placing his ear to the surface of the lake, and distinctly heard the sound of a subterranean fall. “It is there,” said he, rising, “there that the water is discharged, there, doubtless, through a passage in the massive granite that it goes to join the sea, through cavities which we will be able to utilize to our profit! Well! I will find out!” The engineer cut a long branch, stripped off its leaves, and, plunging it down at the angle of the two banks, he found that there was a large open hole a foot below the surface. This was the long-sought-for outlet, and such was the force of the current that the branch was snatched from his hands and disappeared. “There can be no doubt of it now,” repeated the engineer. “It is the mouth of the outlet, and I am going to work to uncover it. “How?” inquired Spilett. “By lowering the lake three feet.” “And how will you do that?” “By opening another vent larger than this.” “Whereabouts, Cyrus?” “Where the bank is nearest the coast.” “But it is a granite wall,” exclaimed Spilett, “Very well,” replied Smith. “I will blow up the wall, and the waters, escaping, will subside so as to discover the orifice—” “And will make a waterfall at the cliff,” added the reporter. “A fall that we will make use of!” answered Cyrus. “Come, come!” The engineer hurried off his companion, whose confidence in Smith was such that he doubted not the success of the undertaking. And yet, this wall of granite, how would they begin: how, without powder, with but imperfect tools, could they blast the rock? Had not the engineer undertaken a work beyond his skill to accomplish? When Smith and the reporter re-entered the Chimneys, they found Herbert and Pencroff occupied in unloading their raft. “The wood-choppers have finished, sir,” said the sailor, laughing, “and when you want masons—” “Not masons, but chemists,” interrupted the engineer. “Yes,” added Spilett, “we are going to blow up the island.” “Blow up the island?” cried the sailor. “A part of it, at least,” answered the reporter.